It has been recently proposed in view of probable petroleum depletion to perform gasification using, as raw material, petroleum coke which is residue in petroleum refinery and/or any resource currently not efficiently utilized such as oilsand, bitumen, brown or other low-quality coal or other fossil fuel, biomass and/or tire chips so as to produce and efficiently utilize a gasification gas comprising hydrogen, hydrocarbon and the like.
FIG. 1 schematically shows an example of a gasification equipment for production of the gasification gas, which is of a twin column type comprising gasification and combustion furnaces 1 and 2. Water vapor 3 is fed to a bottom of the gasification furnace 1 to form a fluidized bed of a bed material 4 (silica sand, limestone, etc.) for gasification of a raw material 5 (coal, biomass, waste plastics, etc.) charged into the fluidized bed, a resultant gasification gas 6 being fed to a gas refining system.
The bed material 4 in the gasification furnace 1 overflows, together with unreacted char 7 produced in the furnace 1, through a duct 1a on the furnace 1 into the combustion furnace 2 where the bed material 4 is blown up by air 8 introduced to a bottom of the furnace 2 with the char 7 being burned to heat the bed material 4.
A combustion exhaust gas 9 blown up together with the bed material 4 in the combustion furnace 2 is introduced through a top of the furnace 2 into a cyclone 10 where the bed material 4 is separated and returned via a downcomer 11 to the gasification furnace 1 while the combustion exhaust gas 9 is taken through a top of the cyclone 10 and fed to an exhaust gas treatment system.
When a rate of the char 7 flowing from the gasification furnace 1 into the combustion furnace 2 runs short, the furnace 2 is fed with an auxiliary fuel F such as coal to keep constant a temperature of the bed material in the furnace 2 or a temperature in the top of the furnace 2.
Disposed between the gasification and combustion furnaces 1 and 2 and between the furnace 1 and the downcomer 11 are seals 12 and 13, respectively, in the form of U-shaped ducts for prevention of the gasification gas from being transported.
Prior art literatures on a gasification equipment relevant to the invention are, for example, Patent literatures 1, 2 and 3.